SH-4 Prolog and Epilog Code Examples (Windows CE 5.0)

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The following code examples show how to use prolog and epilog to perform certain tasks.

• Allocate a stack frame to save R14, R8, and PR

  This example allocates a stack frame to save R14, R8, and PR, and to allow alloca() calls. It also allocates a 4-word argument build area. Local variables and temporaries do not need stack space.

  NESTED_ENTRY Function
  
  mov.l R14, @-R15 // Save old frame pointer.
  mov.l R8, @-R15 // Save a permanent register.
  sts.l PR, @-R15 // Save return address.
  mov  R15, R14  // Set up new frame pointer.
  add  #12, R14
  add  #-16, R15  // Allocate argument save area
  
  PROLOG_END
  
  // Routine body
  
  add  #-12, R14  // Find base of RSA.
  mov  R14, R15
  lds.l @R15+, PR  // Restore return address.
  mov.l @R15+, R8  // Restore R8.
  rts        // Return.
   mov.l @R15+, R14 // Restore R14.
  
  ENTRY_END Function
  

• Allocate a stack frame for a leaf routine

  This example allocates a stack frame for a leaf routine that requires 40 bytes for local variables and temporaries. It uses permanent registers R8, R9, and R10. This routine has no _alloca locals, so no frame pointer is required.

  NESTED_ENTRY Function
  
  mov.l R8, @-R15
  mov.l R9, @-R15
  mov.l R10, @-R15
  add  #-40, R15
  
  PROLOG_END
  
  // Routine body
  
  add  #40, R15
  mov.l @R15+, R10
  mov.l @R15+, R9
  rts
  mov.l @R15+, R8
  
  ENTRY_END Function
  

• Allocate a stack frame with 64KB of memory

  This example allocates a stack frame that requires 64 KB of memory. It saves argument register R4 to the incoming argument save area, and saves argument register R5 to allocated register R8. No separate frame pointer is required. The segment saves return address and permanent register R8. It declares an exception handler.

  EXCEPTION_HANDLER RoutineHandler
  NESTED_ENTRY Function
  
  mov.l R4, @R15   // Save argument to incoming argument save area.
  mov.l R8, @-R15
  sts.l PR, @-R15
  mov.l @(0x0000001C,pc),r1 // Load constant -65528.
  add     r1,r15      // Allocate stack frame.
  mov.l R5, R8      // Save argument to register.
  
  PROLOG_END
  
  // Routine body
  
  mov.l @(0x0000000C,pc),r1 // Load constant 65528.
  add     r1,r15      // Remove stack frame.
  lds.l @R15+, PR      // Recover return address.
  rts
  mov.l @R15+, R8     // Restore R8.
  
  ENTRY_END Function
  

• SH-4 function call

  This example shows an SH-4 function call with permanent floating point register saves and restores. It distributes floating-point arguments to registers, and copies argument registers to allocated registers and the stack.

  NESTED_ENTRY Function
  
  mov.l    r8, @-sp // Store permanent registers.
  mov.l    r9, @-sp
  fmov.s   fr12, @-sp
  fmov.s   fr13, @-sp
  sts.l    pr,  @-sp
  add.l    #-80, sp // Allocate stack frame.
  mov.l    r5, r8 // Move incoming argument registers to 
  fmov.s   fr8, fr13 // allocated registers.
  mov.l    #112, r0  // Spill argument to stack.
  add.l    sp,  r0
  fmov.s   fr6, @r0
  fmov.s   fr7, @-r0
  PROLOG_END
  
  // Routine body
  
  add.l   #80, sp
  lds.l   @sp+,pr   // Restore permanent registers.
  fmov.s   @sp+,fr13
  fmov.s   @sp+,fr12
  mov.l   @sp+,r9
  rts
  mov.l   @sp+,r8
  
  ENTRY_END Function
  

See Also

SH-4 Prolog and Epilog | SH-4 Assembler Macros

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